l 32 ipRGC Flashcards
charactetristics of circadian rhythms
endogenous 24 hour cycle
present in animals and plants
regulates timing of physiological processes: hormone production, metabolism, sleeping/feeding
what controls the phase of circadian rhythms
light detected in retina
- important but not critical for behavior
- phase shifts cycle
what happens to mice activity in the absence of light
still keeps 24 hour cycle but shifts
circadian rhythms in absence of rod/cone
circadian cycles are maintained in the abscence of rod and cone photoreceptors
- rdta/cl KO
pulse with light of differnt intensities and still undergo phase shift similar to WT
- some sensitivity to retina but isnt photoreceptors
SCN
within hypothalamus: ganglion cells send axons down optic nerve and project to different areas
- if you remove SCN you lose entrainment
cobalt VS other drugs
drugs: block photoreceptor input
- potential that there is other input ex. mediated by ATP
cobalt: blocks ALL synaptic transmission so shows that response is intrinsic
intrinsically photosensitive
response in abscence of synaptic transmission means that it must be intriniscally photosensitive
how did they label these RGC
retrograde labelling: injected into SCN and followed back
- made recordings to measure physiology of cell and recovered morphology
depolarization and light intensity
the brighter the stimulus the stronger the response
- depolarization corresponds to light intensity
optimal wavelength
around 480nm, surprising bc not optimal wavelength for other opsins (flavin) in rods/cones
log irridance: increase regardless of wavelength but can still see where is optimal or not
resposne kinetics
very slow adapting and sustained - over a number of minutes
- need this for sensing daylight, dont want to adapt out
targets for ipRGVC
SCN, SPZ, pSCN, MA, IGL, PAG, OPN
role of SCN on brain activity
modulates melatonin in pineal gland
change light content and you can change alertness
